System and method for ophthalmic lens manufacture

ABSTRACT

A method and system for the manufacture of ophthalmic lenses comprising a computer ( 102 ) and a CNC machining platform ( 104 ) in operative connection with the computer. The CNC machining platform includes a mounting stage ( 110 ), a block ( 106 ) in releasable connection with the mounting stage, and a machining tool ( 112 ). When an unfinished lens blank ( 108 ) is properly mounted on the block, the computer is operative to direct the CNC machining platform to perform both back surface generation and patternless edging of the lens blank in one machining cycle. The computer is further operative to direct the CNC machining platform to machine a lap tool for each lens and machine a block for receiving each lens. The block is machined by the platform to include scribe lines for facilitating proper alignment of lens blank.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application SerialNo. 60/176,658 filed Jan. 18, 2000.

TECHNICAL FIELD

This invention relates to the manufacture of ophthalmic lenses.Specifically this invention relates to a new system and method forsurfacing, edging and finishing ophthalmic lenses.

BACKGROUND ART

In the art of ophthalmic lens manufacture, a finished ophthalmic lens isusually made from finished uncut lenses or from semi-finished lensblanks. Finished uncut lenses are lenses that are optically finished onboth front and back surfaces and only need to be edged to the propershape and edge contour to become finished lenses. Most opticallaboratories keep an inventory of single vision finished uncut lenses invarious powers, sizes, and materials to take care of most of the morecommon single vision ophthalmic lens prescriptions.

Semi-finished lens blanks have optically finished front surfaces;however, the back surfaces of these blanks need to be generated andfined and are then either polished or coated to produce finished uncutlenses. Finished uncut lenses are then edged to the proper frontal shapeand edge contour to fit into spectacle/glasses frames or other mountingstructures. Single vision lenses that are outside the normal range ofinventoried finished uncut lenses and most multifocals are made fromsemi-finished lens blanks. Semi-finished lens blanks are made withvarious front surface curve radii, and have various topographiesincluding spherical, aspheric, hyperbolic, irregular aspheric such asprogressive add lenses, and polyspheric such as executive type segmentedbifocals and trifocals.

To generate a desired prescription for a lens, calculations are requiredto determine the topography of the back surface of a lens. Suchcalculations typically involve variables that include the front surfaceradii of the semi-finished blank, the index of refraction of the lensblank material, prescription values of the desired lens, statutoryvalues regarding minimum lens thickness, and the physical dimensions ofthe frame or mounting structure.

In the art, various means have been devised to accomplish the physicalprocess of producing a back surface of optical quality. Most of thesemethods begin by generating a back surface that approximates the desiredback surface topography and surface smoothness. This approximate surfaceis then fined to a more perfect approximation in both curvature andsurface smoothness. After the appropriate accuracy and smoothness isachieved in the fining process, the surface is then polished or surfacecoated to produce a surface of optical quality. The optically finishedlens blank is then edged to the proper shape and edge profile to fitinto the frame for which it was made.

Many business entities that sell ophthalmic lenses do lens finishing asa profit center activity and as a way to expedite delivery of singlevision lenses. Only a small percentage of these entities also dosurfacing of ophthalmic lenses. The business volume of most of theseentities cannot justify the costs of acquiring and operating a surfacinglaboratory. Surfacing laboratory setup costs have heretofore beenseveral times the cost of setting up a laboratory for edging only.

Hiring qualified technicians for ophthalmic lens finishing or trainingpersonnel to perform ophthalmic lens finishing is relatively easy.However, hiring and training optical technicians to operate a surfacinglaboratory is not easy. In many communities it is very difficult to findpersonnel that are trained in surfacing. Technicians who are qualifiedto do surfacing are generally remunerated at higher pay scales thantechnicians skilled only in optical finishing.

In addition to the significantly higher equipment and personnel costs ofa surfacing lab, there are also higher ongoing costs for the additionallab space required. At least several hundred square feet of operationalspace and storage space have heretofore been required for a full servicesurfacing and edging ophthalmic lens laboratory. Consequently there is aneed for a system and method of ophthalmic lens manufacture that wouldsignificantly reduce the investment required to acquire a surfacing andedging laboratory. There is a further need for a system and method ofophthalmic lens manufacture that significantly reduces the costsassociated with operating a surfacing and edging laboratory. Further,there is a need for a system and method of ophthalmic lens manufacturethat is operative to perform surfacing and edging by an operator withlittle skill in the art.

In the prior art, the processes of surfacing and edging are done on atleast two separate machines. In the prior art, blocking for surfacingand edging required two separate blocking devices. Also in the priorart, the individual processes of lap tool surfacing and lens cribbingand safety beveling and edge grooving and edge polishing and lensengraving each requires its own machine or device or machineaugmentation. Each of these machines or devices or augmentations is tovarying degrees expensive to acquire and each of the machines or devicesrequires laboratory space. Each of these operations, if done by hand,requires the necessary acquisition of skills and application of thoseskills in order to perform the various operations. Consequently, thereis therefore a need for a system and method of ophthalmic lensmanufacture that reduces the need to employ a plurality of expensive andcomplex machines to manufacture lenses.

In the prior art, after a semi-finished lens blank is generated andfined and polished it is de-blocked and inspected and then laid out andblocked again for edging. Blocking for surfacing and blocking for edgingare two different procedures that differ in significant ways requiringtwo different sets of skills and requiring two separate and verydifferent mechanical blocking systems. Repeating the blocking process isnecessary in part because the metallic block used for surfacing couldinterfere with the edging process. This is because portions of the uncutlens that lie under the surfacing block frequently need to be removedduring the edging process. If the standard surfacing block were alsoused during edging, this could result in the metal surfacing blockcoming into contact with the cutting or grinding surfaces of the edgingmachine thereby damaging the cutting or grinding surfaces of the edgingmachine and damaging or destroying the block in the process.Additionally, the need to block a lens twice multiplies theopportunities for error and spoilage and requires the expenditure oftime. Consequently there is a need for a method of ophthalmic lensmanufacture that eliminates the need to block a lens blank twice forthose lenses that require both surfacing and edging.

The prior art describes several types of single point blocking systems.One type describes centering the block on the point of the lens thatwould occupy the geometric center of the frame when the lens is finished(frame geometric center blocking). Another describes centering the blockon the point of the lens that would occupy the optical center of thefinished lens (optical center blocking). A third describes centering theblock in the geometric center of the semi-finished uncut lens (lensblank geometric center blocking). In prior art, all three of methods areoptimized for surfacing by tilting the front surface by the properamount and in the proper direction to move the optic axis into alignmentwith the generator feed axis. Only in the case of “frame geometriccenter blocking” is it possible to optimize for edging. Thisoptimization for edging is accomplished by aligning the front surfacenormal at the geometric center with the feed axis of the generator.

The “optical center” and “lens blank geometric center” blockingarrangements create relationships between a lens blank and the generatorfeed axis that are optimal for generating lens back surfaces becauseerrors in thickness at any stage in the process of surface generationand fining will not affect a change in the position of the opticalcenter of the lens. This is because the optic axis does not move as thethickness of the blank decreases. However, in neither of these two casesare the blocking arrangements optimal for edging a lens. In bothinstances the lens is frequently tilted too much to apply an edgeparallel to the normal at the geometric center of the front surface ofthe finished lens. Applying an edge to a lens at any angle other thanparallel to the front surface normal at the geometric center results inedges that are skewed and frequently thicker than necessary and withedge beads that have less than optimal orientations.

A blocking system optimized for edging, like “frame geometric centerblocking”, wherein the lens blank is blocked on the geometric center ofthe finished lens and where the normal at the geometric center of thefront surface of the finished lens is parallel to the axis of rotationof the edging tool or edge grinding wheel, is not optimal for surfacing.Except for the relatively rare case where there is positionalcoincidence between the optical center of the lens and the framegeometric center of the lens, the optical center of the lens is made tomove or “creep” as the lens is made to decrease in thickness duringfining.

A method of lens blocking that is optimized for edging and that is alsooperative for surface generation would be of considerable utility. Itwould allow for a single blocking step for both the surface generationof a lens and for the edging of that lens without de-blocking andre-blocking between the steps of surface generation and edging.Therefore there is a need for a system and method of blocking a lens forboth surfacing and edging that reduces the problems associated withoptical center creep.

Prescription lenses for patients are often generated in pairs for aspectacle frame. Prior art systems typically generate each lensindependently. Production cycle times for generating lenses may bereduced by employing multiple surfacing and edging machines in thelaboratory to generate pairs of lenses simultaneously, howeverduplication of equipment doubles the acquisition and operational costsof the laboratory. Thus there exists a need for a system and method ofophthalmic lens manufacture that provides for reduced production cycletimes for pairs of prescription lens without significantly increasingcosts for the laboratory.

Heat transfer into the lens blank from the heated blocking medium duringthe blocking procedure is a frequent cause of so called “lens warpage”.The greater the amount of heat transfer involved and the more uneven thedistribution of that heat transfer is, the greater the chance ofproducing warpage and ruining the lens or producing a substandard lens.There is therefore a need for a method of ophthalmic lens manufacturethat could minimize the transference of heat into the lens blank duringblocking, and that could make the distribution of that heat transferenceuniform over the entire area of the finished lens. Further, there is aneed for a system and method of ophthalmic lens manufacture that couldeliminate problems associated with heat transfer into the lens duringblocking.

The standard block used for lens surfacing is generally smaller than thesize of the finished lens being fabricated. The portion of a lens thatremains unsupported can undergo flexure when submitted to the forcesinvolved in the generating, fining and polishing processes. This resultsin flaws or “waves” in the optics of the lens in the areas thatunderwent the flexure and is a common source of spoilage or ofsubstandard lenses. Consequently, there is a need for a technique thatwould eliminate these optical flaws caused by flexion of the lens blankduring generating and fining and polishing of the lens.

For cosmetic effect, the edges of lenses are sometimes polished. Inprior art, when the edge of the lens has a mounting bevel, the bevel onthe edge of the lens is polished when the edge is polished. Polishingthe mounting bevel reduces the holding friction of the bevel that aidsin holding the lens in the frame, and that holding friction is alsoimportant in resisting rotation of the lens within the frame. For thisreason, a lens that has a polished edge with a polished bevel is moredifficult to keep securely mounted and properly oriented in its frame.There is therefore a need for a system and method of ophthalmic lensmanufacture that is operative to polish the edge of a lens withoutpolishing the mounting bevel on the edge of the lens.

Prior art systems for lens manufacture are inherently non-mobile, due tothe large amounts of laboratory space required to store an inventory oflap tools and the many pieces of heavy laboratory equipment needed togenerate and surface and finish lenses. Thus, prior art systems cannotbe easily transported to locations such as factories to manufacturesafety lenses on-site or military theaters to support the optical needsof military personnel. Consequently, there is a need for an ophthalmiclens manufacturing system that is portable.

DISCLOSURE OF INVENTION

It is an object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatsignificantly reduces the costs of acquiring and operating a fullservice surfacing and edging ophthalmic lens laboratory.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperable with little knowledge of the optical arts by the operator.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatrequires little physical laboratory space.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to perform both lens surfacing and lens edging.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatrequires only one lens blocking operation to perform both surfacing andedging.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to block a lens for both surfacing and edging that isoptimized for both the minimization of edge thickness and thecompensation of optical center “creep.”

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that doesnot require complicated rotating or tilting of the semi-finished lensblank when blocking for surfacing.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to perform both lens surfacing and lens edging in one machineoperation.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatutilizes a single tool with multiple cutting surfaces capable of bothsurface generation and edging of lenses.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that doesnot require a lap tool library.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that doesnot require a lap tool library but is capable of using a lap toollibrary.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that doesedging and surfacing of lenses and lap tool surfacing on the samemachine.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to generate the precise lap tool for each lens manufactured.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to generate the precise mounting blocks for each lensmanufactured.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to generate the precise mounting blocks for each lensmanufactured with scribe marks applied to the surface of the blocks tofacilitate alignment for blocking.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to perform surfacing of both lenses of a pair of lenses at thesame time.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to perform edging of both lenses of a pair of lenses at thesame time.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to perform lap tool surfacing of two lap tools at the sametime.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatminimizes the transference of heat into the lens blank during blockingand that makes the distribution of that heat transference uniform overthe entire area of the finished lens.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thateliminates the transference of heat into the lens blank during blocking

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thateliminates fabrication flaws caused when unsupported portions of a lensblank flexes under the forces incurred during the generating, fining,and polishing processes.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture thatprovides for easy visual verification of proper blank size.

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isoperative to polish the edge of a lens without polishing the mountingbevel on the edge of the lens

It is a further object of the exemplary form of the present invention toprovide a system and method for ophthalmic lens manufacture that isportable.

Further objects of the present invention will be made apparent in thefollowing Best Modes for Carrying Out Invention and the appended claims.

The foregoing objects are accomplished in one exemplary embodiment ofthe invention by a system and method for ophthalmic lens manufacturethat employs computer numerically controlled (CNC) machining techniquesthat are operative to generate and edge semi-finished lenses and to edgefinished uncut lenses.

An exemplary embodiment of the present invention relies on the fact thatthe topographies of optical surfaces are very well defined. If thespatial coordinates (x,y,z) of any three points on a lens front surfaceare known within a coordinate system, then the spatial coordinates ofall other points on the front surface can be derived within thecoordinate system.

Further, if the center thickness and position of the optical center of alens are known, then the spatial coordinates of any point on the backsurface of that same lens can be derived. Further still, if a sufficientnumber of planar coordinates (x,y) representing the shape of the frameinto which the lens will be mounted are known relative to the positionthat the lens geometric center will occupy within the frame and if theoffset from the front surface of the mounting groove or bevel is known,then the finished shape and contour of the lens can be accuratelyderived including the position of the mounting bevel or groove.

The exemplary embodiment of the present invention includes a CNCmachining platform that is operative to direct an appropriate tool toperform both surfacing and edging of a lens blank. The system includes acomputer that is operative to retrieve frame coordinates of the lensreceiving portion of a spectacle frame. In the exemplary embodiment theframe coordinates are stored in a data store in operative connectionwith the computer. In one exemplary embodiment of the present inventionthese frame coordinates are acquired by tracing the inner circumferenceof the frame apertures with a graphics tablet, or other scanning devicein operative connection with the computer.

The computer is also in operative connection with an input device and adata store. A user of the system inputs with the input deviceprescription specifications for the desired lens. The data storeincludes a plurality of front surface data values that correspond to thefront surface topography of the lens blank. The computer calculates toolpaths for machining the lens blank with the tool responsive to the framecoordinates, the front surface data values, and the prescriptionspecifications.

These tool paths are calculated with respect to the reference frame ofthe machining platform. The machining platform is operative to directthe tool to move with respect to the lens blank according to thecalculated machining tool paths.

The system is further operative to generate an appropriate lap tool forfinishing the generated lens. The machining platform is operative tomachine the surface of the lap tool responsive to the front surface datavalues, the prescription specifications, and, in cases where frontsurface radii are shorter than back surface radii, the data representingthe size and shape of the frame. The orientation of the lap tool axesmay be machined to match the orientation of the axes in the final lensso there is no need to rotate the lens blank in the surface blockingprocess in order to align the lens axes with the lap tool axes. There isalso no need for prism blocking or prism ring tilting of the blockedlens blank for back surface generation.

The system is further operative to machine an appropriate block forreceiving the front surface of the lens responsive to the front surfacedata, frame data, and prescription specifications, which include theinterpupillary distance (Pd). In the exemplary embodiment the block ismachined to include scribe lines that are used by an operator toproperly position and align the lens blank so that all points on thefront surface of the lens blank can be determined relative the referenceframe of the block and the machining platform.

Further objects of the present invention will be made apparent in thefollowing Best Modes for Carrying Out Invention and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1-3 show exemplary method steps of the present invention forgenerating an ophthalmic lens from a lens blank.

FIG. 4 is a schematic view representative of an exemplary system of thepresent invention for generating an ophthalmic lens from a lens blank.

FIG. 5 shows exemplary machining tools that are operative to performboth surfacing and edging.

FIGS. 6 and 7 show exemplary machining tools machining the edge of alens blank.

FIG. 8 show an exemplary machining tool machining the back surface of alens blank.

FIG. 9 shows an exemplary machining tool machining the finishing surfaceof a lap tool.

FIG. 10 shows further exemplary machining tools of the presentinvention.

FIG. 11 shows an exemplary block for the present exemplary invention

FIG. 12 shows a lens blank mounted to the exemplary block of the presentinvention

FIG. 13 shows the relative locations of exemplary markings for blockinga lens blank.

FIG. 14 shows a side cross-sectional view of an exemplary block.

FIG. 15 shows a side cross-sectional view of an exemplary block that hasbeen machined to receive a lens blank with the lens blank positioned onthe block.

FIG. 16 shows a top plan view of a lens blank positioned on the machinedblock.

FIG. 17 shows a top plan view of the lens block with scribe lines in theshape of a bifocal segment.

FIG. 18 shows a side cross-sectional view of a lens blank mounted on anexemplary block.

FIG. 19 shows an alternative exemplary system for blocking a lens blank.

FIG. 20 shows a perspective view representative of an exemplarymachining platform of the present invention.

FIG. 21 shows a perspective view representative of an exemplarymachining platform of the present invention with the mounting stagerotated to an upward position.

FIG. 22 shows a top plan view of an alternative exemplary machiningplatform of the present invention.

FIG. 23 shows a front plan view of the alternative exemplary machiningplatform.

FIG. 24 shows a side plan view of the alternative exemplary machiningplatform.

FIG. 25 is a schematic view representative of a further alternativeexemplary system for simultaneously generating both the right and leftlenses for spectacles frames.

FIG. 26 shows the relative orientation of the x ball slide, y ballslides, and z ball slides for the further alternative exemplarymachining platform.

FIG. 27 shows two exemplary orientations of a mounted lens blank withrespect to the relative feed axis of a tool for edging the lens blank.

BEST MODES FOR CARRYING OUT INVENTION

Referring now to the drawings and particularly to FIG. 1, there is showntherein exemplary method steps of the present invention for generatingan ophthalmic lens. Here the exemplary method comprises the step 10 ofacquiring or collecting and temporarily or permanently storing dataabout the size and shape of the lens receiving aperture of a spectacleframe or other mounting structure, or alternately about the finishedlens circumference and frame shape. In the exemplary embodiment framedata is collected in the form of a plurality of planar points (x,y)relative to a planar coordinate system.

The exemplary method further comprises the step 12 of acquiring orcollecting and temporarily or permanently storing prescriptionspecifications for the desired ophthalmic lens being generated from thelens blank. For the present exemplary invention, the prescriptionspecifications includes information which describes the opticalcharacteristics for the finished ophthalmic lens and physicalcharacteristics of the finished ophthalmic lens including the materialof the lens, the minimum thickness of the lens, and the contour of thelens edge (bevel or groove). Such information can be acquired by a userinputting the desired prescription specifications for the lens. In analternative embodiment, the prescription information can be acquiredfrom a data store.

In Step 14, the exemplary method includes selecting and acquiring theappropriate lens blank responsive to the prescription specification andframe data. In one embodiment of the present invention, a human machineinterface (HMI) is operative to identify which lens blanks areappropriate from a data store of different types of lens blanks. Thisdescribed embodiment may also include an inventory system of lens blanksthat are available from inventory for the laboratory. The operator maythen select from inventory at least one of the lens blanks that havebeen identified by the HMI as being in stock.

The exemplary method further comprises the step 16 of acquiring orcollecting and temporarily or permanently storing data about the opticalproperties of the lens blank. The optical properties include the frontsurface topography of a lens blank and the index of refraction of thematerial comprising the lens blank. This data acquisition and storagecan be done at any point in time prior to the actual manufacturingprocess. This lens front surface data is stored in a form and formatthat is operative to return a “z” value for any “x,y” coordinate query.In the exemplary embodiment when the prescription data values indicatethat the front surface on the lens blank is spherical, these spatialcoordinates can be acquired by calculation. When the prescription datavalues indicate that the front surface of the lens blank is aspherical,the front surface coordinates can be acquired from a data store of frontsurface topography information responsive to the type of aspheric lensbeing machined. It should be noted that front surface coordinates forspherical lens blanks may also be acquired from surface data storedpreviously acquired or calculated and stored in a data store. In analternative embodiment the front surface topography information can beacquired directly with a scanning device. Within the described exemplaryembodiment of the invention, the data stores that hold topographicalinformation are also operative to return information about the locationsof lens blank front surface artifacts such as factory markings orbifocal segment lines that may be used for lens blank alignment duringblocking.

This described exemplary embodiment of the invention may further includesteps for generating a lap tool that is operative for fining andpolishing the machined back surface of the lens. In step 18 the presentexemplary method includes calculating machining tool paths for machiningthe lap tool with an appropriate machining tool of the CNC machiningplatform. The machining tool paths for the lap tool are calculatedresponsive to the front surface data, prescription specifications of themachined lens that will be fined and polished with the finished laptool, the frame data in some cases, and the thicknesses of the finingand polishing pads. In step 20 the method includes mounting the lap toolblank on the machining platform and in step 22 the method includesmachining the lap tool surfaces responsive to the calculated machiningtool paths to produce the finished lap tool.

The exemplary method further comprises the step 24 of calculating amachining tool path for an appropriate tool for machining the topsurfaces of a block for receiving the front surface of the selected lensblank. The machining tool paths are also calculated for machiningalignment scribe lines or other alignment features onto an upper surfaceof the block, which are used by the operator in properly aligning theselected lens blank on the block. These tool paths are calculatedresponsive to the type of lens blank selected, the positions ofartifacts on the lens surface that may be used for lens blank alignmentpurposes, the frame size and shape data, the front lens surfacetopography data, and the prescription specifications. In addition, themachining tool paths are calculated for machining the top surfaces ofthe block so as to support the portion of the front surface of the lensblank that will become the finished lens. A block machined in thismanner will have 1) a top surface that mates with the front surface ofthe lens blank when the blank is properly aligned and 2) surfacealignment scribe lines to facilitate lens blank alignment, and 3) theshape of the finished lens outline sculpted into the face of the block.

In step 26 the exemplary method further comprises the step 26 ofmounting a block on the CNC machining platform and the step 28 ofmachining the top surface of the block with the appropriate toolresponsive to the calculated tool paths. The machined block is operativeto receive the front surfaces of the selected lens blank such that whenthe lens blank is aligned according to the machined scribe lines, allpoints on the front surface of the lens blank are known with respect tothe reference frame of the CNC machining platform.

In step 30, the method includes identifying landmarks on the lens suchas a bifocal segment or temporary marks on the lens blank that are usedto align the lens blank with the scribe lines on the block. This stepmay also include marking up the lens blank if necessary with thetemporary alignment and positioning marks responsive to instructionsfrom the HMI.

In step 32 the exemplary method includes blocking the lens. Thisexemplary blocking step includes affixing a thin transparent plasticfilm, with adhesive on both sides, onto the surface of the lens blank,aligning the appropriate landmarks on the lens blank with the scribelines on the block, and securely bonding the lens blank to the block byapplying appropriate pressure to the back of the lens blank.

By generating custom blocks for each lens blank, the procedures forblocking the lens are greatly simplified. These machined scribe linessignificantly reduce the need for a laboratory technician to measure andplace complex alignment and positioning markings on the surface of thelens blank. The scribe lines are positioned to correspond to readilyidentifiable landmarks on the lens block such as a bifocal segment line.For lenses that do not have readily identifiable landmarks, the scribelines may be positioned to correspond to markings on the lens blank thatare relatively easy to make by an operator. For example reference markscould be placed on the optical center of the lens blank and two otherpoints or a line could be placed along some readily identifiable axis ofthe lens blank. The custom machined block for such a lens would includescribe lines, which correspond to the optical center and axis markings.Additionally, since the shape of the final lens is sculpted into theface of the block, visual verification of the proper blank size isreadily made.

Once a lens blank has been blocked in this manner, all of the spatialcoordinate points (x,y,z) on the front surface of the lens blank can bedetermined with adequate certainty relative to the coordinate system ofthe machining platform when the blocked lens is mounted on the machiningplatform.

The exemplary method further comprises the step 34 of calculating amachining tool path for an appropriate tool for machining the backsurface and edge of the lens blank. The tool paths are calculatedresponsive to the frame data, front lens surface data and other physicalproperties of the lens blank like the index of refraction, andprescription specifications. In step 36 the method includes mounting theblocked lens on the machining platform. In step 38 the method includesmachining the lens blank responsive to the calculated tool paths with anappropriate tool in operative connection with the CNC machiningplatform. The back surface of the lens blank is machined to produce alens blank that is ready for the fining and subsequent polishing orcoating processes that may be required to finish the back surface of thelens blank into an optical lens surface. The edge of the lens blank ismachined for insertion into the spectacle frame for which the lens blankis being fashioned to fit. Step 38 may also include edge polishing andsafety beveling the lens and edge grooving and engraving of the lens.

Once the lens blank has been machined, the exemplary method further, ifrequired, comprises the step 40 of fining and polishing the unfinishedsurfaces of the lens with the lap tool machined in step 22 to produce anoptical lens surface. In step 42 the exemplary method includesde-blocking, cleaning, and inspecting the finished and edged lens. Instep 44 the exemplary method includes inserting the lens into thespectacle frame and inspecting the lens and frame combination.

It is to be understood that the method steps described above areexemplary only. In this and in alternative embodiments other methodssteps and/or a differing order of these method steps may be performed tocarry out the exemplary embodiments of the present invention. Inaddition the exemplary method may be performed with a system that isoperative to generate one or more optical lenses simultaneously

FIG. 4 shows a schematic view representative of an exemplary system thatis operative to generate ophthalmic lenses according to the previouslydescribed method. Here the system 100 comprises a computer 102 and a CNCmachining platform 104 in operative connection with the computer. TheCNC machining platform 104 includes a mounting stage 110, a mountingblock 106 in releasable connection with the mounting stage, and a tool112. An exemplary lens blank 108 is shown mounted to the block 106. Thecomputer is further in operative connection with an input device 114, adisplay device 116, and a data store 118. Examples of operative inputdevices for this exemplary embodiment include a keyboard, mouse, touchscreen, trackball, voice recognition system, or any other device that isoperative to input signals into the computer. Examples of operativedisplay devices for this exemplary embodiment include a CRT monitor, LCDdisplay, or any other output device that is operative to displayinformation concerning the operation of the system 100. Examples ofoperative data stores 118 for the exemplary embodiment, includerelational databases, flat files, CD's, DVD's, memory arrays or anyother device or structure that is operative to temporarily orpermanently store information. The data store 118 may also encompass acombination of these different types of devices or structures. The datastore 118 is operative to store frame data values that correspond to thelens receiving apertures for a plurality of spectacle frames. The datastore 118 is further operative to store physical properties for aplurality of lens blanks. Such physical properties for example includedata which describes the front surface topographies of the lens blanksand the index of refraction of the lens blanks. The physical propertiesdata may further include the blank diameter, the blank edge thickness,the blank center thickness, the locations of front surface artifacts,and any other useful attribute of the lens blank. Exemplary tools 112 ofthe present invention encompass machining tools that are operative toremove material from a mounting block or lens, including a grindingwheel, a lathing tool, or any other tool that is operative for cutting,grinding, drilling, scratching, and polishing structures mounted to themounting stage.

In an alternative exemplary embodiment of the present invention, thesystem 100 further comprises a graphics tablet 119, optical scanner orother device that employs spatial digitizing technology, in operativeconnection with the computer. The graphic tablet or other similardigitizing device is used to acquire spatial coordinates for theaperture receiving portion of a lens by enabling an operator to manuallytrace the inner circumference of the frame aperture on the graphicstablet. These frame aperture coordinates are then stored in the datastore 118.

The computer includes an appropriate software application and/orfirmware that is operative to control the movement of the tool 112 withrespect to the mounting stage 110. The software application is furtheroperative to have the computer output with the display device 116information concerning the operation of the system 100. In addition thesoftware application is further operative to prompt a user of the systemto input prescription information for a desired lens being generatedwith the system.

In one exemplary embodiment the mounting stage 110 responsive to thecomputer 102 is operative to move the mounting block 106 and lens 108relative to the feed axis of the tool 112. As shown in FIG. 27, therelative feed axis 714, 716 of a tool 710, 712 corresponds to the vectoralong which the tool 710, 712 moves toward or away from the lens blank108 and mounting block 106. In this exemplary embodiment, the lens blank108 is mounted to the block 106 such that the axis of rotation 704 ofthe block is coincident with the front surface normal 702 at thegeometric center 708 of the portion 706 of the lens blank that willremain after edging the lens blank to fit within the lens receivingportion of the spectacle frame. Also in this exemplary embodiment a tool710, 712 is positioned for edging the lens blank 108 such that relativefeed axis 714, 716 of the tool is generally parallel to the frontsurface normal 702 at the geometric center 708 of the portion 706 of thelens blank that will remain after edging.

For alternative exemplary embodiments of the present invention and forexemplary embodiments of the present invention in which the mountingstage does not rotate the block, the lens blank may be mounted such thatthe front surface normal at the geometric center of the portion of thelens blank that remains after it is edged to fit the receiving portionof the spectacle frame, is orientated generally parallel to the feedaxis of the tool used for edging the lens blank.

To aid an operator with mounting a lens blank in this describedexemplary orientation, the exemplary embodiment of the present inventionis operative to machine the block to include alignment features in anupper surface of the block which provide a visual and/or structuralguide for aligning the lens properly. When the lens blank 108 is blockedin these described exemplary orientations, the relative location forspecific points on the lens blank can be determined by the computersystem 102 relative the coordinate system of the mounting stage, blockand/or tool. Further, the computer 102 is operative to direct one ormore tools to machine both the back surface and the edge of the lensblank 108 responsive to the stored frame data values, the storedphysical properties for the lens (including front surface topographydata), and the inputted prescription information. In addition byblocking the lens blanks in the described orientations, the lens blankdoes not need to be re-blocked between surfacing and edging operations.Also the exemplary orientation of the lens blank relative the tool usedfor edging is operative to minimize edge thickness for the finishedlens.

FIG. 5 illustrates several possible profiles for rotary cutting toolscapable of performing both surfacing and edging. These exemplary toolshave radiused end cutting surfaces 130 and side cutting flutes 132.Cutting tool 120 includes a V-bevel 134 with flat edges 136. Cuttingtool 122 includes a V-bevel 138 with tapered edges 140. Cutting tool 124includes a modified Hide-A Bevel 142. Cutting tool 126 includes aV-bevel 144 with groover 146 for nylon chord mounted lenses.

Although these exemplary machining tools include end cutting surfaces(Radiused ends) 130 and side cutting surfaces (side flutes) 132 thatcome together at the junction of the two cutting edges, it is to beunderstood that the present invention also encompasses machining toolswith machining end surfaces and side machining surfaces that are not soadjoined.

In the exemplary embodiment, the side flutes 132 are used for edginglenses. FIG. 6 depicts an exemplary tapered V-bevel rotary cutting tool122 that is edging a V-beveled lens 150. FIG. 7 shows an exemplary flatedge grooving rotary cutting tool 126 edging a grooved lens 152. Also inthe exemplary embodiment, the radiused ends 130 are used to generatelens surfaces and for cutting lap tool surfaces and for surfacing lensmounting blocks. FIG. 8 shows the radiused end 130 of a flat edged tool120 making a surfacing pass 156 over a pre-edged lens 154. FIG. 9 showsthe radiused end of the tool 120 making a machining pass 158 forsurfacing a lap tool 160. Using tools fashioned in this or similarmanner makes possible the use of a single CNC platform to perform boththe surfacing and edging of lenses and also to perform the surfacing oflap tool blanks and lens mounting blocks.

FIG. 10 shows additional exemplary tools 502, 505, and 508 of thepresent invention. Tool 502 includes an angled V-bevel edging surface503 which tapers to a relatively narrower radiused end 504. Tool 505includes a single point tool tip 511 that is operative for surfacing.Tool 506 includes a foreshortened tip radius 509 which eliminatesportions of a full radius of the tool 510 which is unneeded forsurfacing. In addition the shorter tip radius 509 reduces the “draft” ordepth below the edge bead of the lens being milled. As a result asmaller thinner lens block may be used. Tool 507 includes a replaceableend 508 that may accommodate a plurality of different machiningsurfaces. For example, the exemplary tool 507 includes a removablegrooving portion 513. In one exemplary embodiment the replaceable end508 may include a threaded portion that is received by the body of thetool 507.

The exemplary tool 507 further includes a polishing surface portion 514that is operative for edge polishing. The exemplary polishing surfaceportion 514 further includes a recessed portion 512 that may be placedadjacent the beveled surfaces of a lens. The recessed portion 512prevents the beveled edge from being polished by the tool 507 so thatthe lens is less likely to slip when mounted within a spectacle frame.

Further exemplary tools may include engraving tips that are operativefor engraving markings on a lens mounting block such as alignmentfeatures, lens identification values, the patients name, cosmeticembellishments, and/or prescription information. Other exemplary toolsmay include features for machining a safety bevel.

In exemplary embodiment of the present invention non-rotating tools mayalso be used to perform machining operations. For example a pointed edgeof a non rotating tool 505 may be used to scratch the surface of thelens blank to form alignment features or other markings. Further, inexemplary embodiments where the mounting stage is operative to rotatethe lens, an exemplary lathing tool may be used to machine the lens.

FIG. 11 is representative of an exemplary reusable or a disposablecustom mounting block 540 of the present invention. As discussedpreviously the exemplary lens mounting block 540 is operative to bemachined to receive a specific lens blank by the exemplary machiningplatform of the present invention. The block 540 includes a supportportion 560 that is adapted for mounting on the mounting stage. Theblock 540 further includes a machineable layer 562 that is shaped by themachining platform to receive the particular type of lens blank thatwill be mounted to the block 540. In the exemplary embodiment themachining layer 562 includes a low melting point wax compound, however,in alternative embodiments the machineable layer 562 may be comprised ofa thermoplastic material, a metallic alloy or any other reusable ordisposable material that may be machined by the machining platform.

The machining platform of the present invention removes blockingmaterial 542 to form an upper surface 544 in the block 540 which isoperative to support generally all of the front surface of the lensblank that will remain after the lens blank is surfaced and edged by theexemplary machining platform. The tool paths for machining the lensblock are calculated responsive to the frame data, the opticalproperties of the lens including front surface topography information,and the inputted prescription data for the ophthalmic lens beinggenerated.

Also as discussed previously the exemplary embodiment the machiningplatform is further operative to place scribe lines 546 or otheralignment features into the upper surface 544 of the block. The scribelines 546 are used by the operator of the machine to properly align thelens blank with the block. FIG. 12 shows a lens blank 550 mounted to theblock 540. In this exemplary embodiment an adhesive layer 548 is placedbetween the lens and lens blank to securely bond the lens blank to theblock. In the exemplary embodiment the adhesive layer 548 is comprisedof a transparent or semi-transparent double-sided pressure sensitiveadhesive film which is placed between the block and the lens blank by anoperator. By pressing the lens blank 550 against the adhesive layer 548an adhesive bond is formed between the lens blank 550 to the block 540.

In alternative exemplary embodiments various other methods may be usedto affix the lens to the block. In one alternative exemplary embodiment,the top surface of the block is exposed to a heat source for a shortperiod of time, melting a very thin layer of the block surface. The lensblank is then aligned and placed onto the molten surface. Re-hardeningof the substrate accomplishes the bond. In this method, the applicationof a protective plastic film, onto the lens surface, significantlyenhances the bonding strength. In another alternative embodiment,semitransparent plastic film is applied to the lens blank surface. Thelens blank is then placed upon the scribed block in proper alignment.This loose assembly is exposed to a light source of appropriatewavelength composition and intensity so that photonic radiation passesthrough the lens blank and is absorbed at the lens-block interface. Thephotonic absorption causes local heating and melting of the surface ofthe block. The melting, surface wetting, and re-hardening that occurs atthe interface accomplishes the bond. To prevent the upper surface fromwarping when heat is applied, cold zones may be created over sufficientportions of block to maintain the overall structural configuration ofthe block. Placing an insulating material or reflecting material betweenselected portions of the block and the heat and/or light source maycreate such cold zones.

In addition to the described bonding mechanisms many other methods ofbonding the lens to the block could be employed including the use ofauto-polymerizing agents or the use of heat activated polymerizingagents or photonically activated polymerizing agents or the use of epoxyresin compounds.

For this described exemplary blocking systems, the lens blank is alignedwith the block by placing the point on the lens blank that will occupythe geometric center of the frame at a fixed location within thecoordinate system of the block and exemplary machining platform. This isaccomplished by marking some point on the lens with a known positionalrelationship to the point on the lens that will occupy the geometriccenter of the frame when finished. It is also necessary to have someaxial reference mark on the lens to represent the 0-180 axis orientationof the lens. FIG. 13 shows a spherical front surface bifocal lens blank250 so marked. In this example, the lens blank 250 is marked at thecenter 252 of the bifocal segment line 254. This point is thenpositioned at the proper location relative to scribe lines 256 or otheralignment features of the block. The segment line 254 also acts as theaxial orientation marker. When the lens blank is aligned with the scribemarkings on the block, the lens blank may be adhesively affixed to theblock by one of the exemplary blocking methods discussed previously.When the lens blank is aligned by this exemplary method, the geometriccenter of the lens will be known relative the coordinate system of theblock and machining platform.

In further alternative exemplary embodiment, the block surface ismachined so that only the outer rim of the block surface contacts andsupports the lens block. A thin cavity is left between the lens frontsurface and the lens blank top surface. Molten blocking medium isintroduced into the cavity to affect the bond between the blank and theblock. FIGS. 14-18 shows this exemplary alternative embodiment.

FIG. 14 shows an exemplary alternative reusable custom block 300. Theblock 300 includes a support portion 302 that is adapted for mounting onthe mounting stage. The block 300 also includes a machineable layer 304that is shaped by the machining platform to receive the particular typeof lens blank that will be mounted to the block 300. In the exemplaryembodiment the machining layer 304 includes a low melting point waxcompound, however, as discussed previously alternative embodiments ofthe exemplary blocks may include a machineable layer 304 comprised of athermoplastic material, a metallic alloy or any other reusable ordisposable material that may be machined by the machining platform.

As shown in FIG. 15, after the block 300 has been machined, a rim 306with the shape of the finished lens with a hollow interior 308 is formedin the machineable layer 304. This rim 306 is generated with a threedimensional contouring that mirrors the front surface topography 312 ofa lens blank that is properly mounted on the block 300. With the block300 machined in this manner, the front surface of the lens touchessubstantially the entire rim 306 of the top of the block. In theexemplary embodiment the width of the rim 306 is about 4 mm. Thisapproximate rim width affords sufficient support for the lens during theblocking procedure and is wide enough so that the rim will not becomedeformed by heat when fresh molten blocking medium is introduced intothe hollow interior 308 during the blocking procedure.

In this described exemplary embodiment the rim 306 is also machined tobe equal to or slightly smaller than the size of the finished lens. Thisprovides working support to the entire surface of the lens blank thatcorresponds to the finished lens. Unlike a preexisting block, no damagewill result to the tool or the block when edging the lens blank becauseno portion of the block extends beyond the portion of the lens blankthat encompasses the finished lens.

In the exemplary embodiment a lens is positioned upon the block 300 sothat the front surface normal at the geometric center of the finishedlens is coincident with the “z” axis of the block coordinate systemthereby placing the lens front surface generally parallel to thereference plane of the blocking system and perpendicular to a relativefeed axis of a machining tool. In the exemplary embodiment, alignmentscribe lines 316 are machined onto the top surface 318 of the block 300.As discussed previously, the scribe lines 316 are used to properly alignthe lens blank. When the lens blank 310 is placed on the block 300, anoperator can properly position the lens blank by aligning landmarks ofthe lens such as bifocal segments and/or other markings on the lensblank with the scribe lines 316.

In the exemplary embodiment, the scribe lines 316 are machined so thatthe space between the scribe lines on the block and the markings orfeatures on the lens front surface are narrow. This close approximationbetween the features or markings on the lens and the matching scribelines on the block ensure that no significant parallax error isintroduced when aligning the lens on the block by sighting directlyabove the lens.

FIG. 16 shows a top plan view of the lens blank 310 properly positionedon the block 300. Here the lens blank 310 includes a bifocal segment320. The block 300 has been machined to include three scribe lines: abase line 322, and two perpendicular lines 324 and 326. To properlyalign the bifocal segment 320, the straight portion of the bifocalsegment 320 is aligned with the base line 322. The left and rightboundary positions of the bifocal segment are aligned between the twoperpendicular lines 324 and 326.

It is to be understood that this described layout of the scribe lines isexemplary only. The present invention includes any pattern of scribelines that are useful for aligning the lens blank properly. For exampleFIG. 17 shows an alternative pattern 328 for the scribe lines that aremachined to correspond to the actual shape of a bifocal segment.Consequently a lens blank can be properly aligned by positioning thebifocal segment to directly overlie the scribe line pattern 328. In theexemplary embodiment the scribe lines are generally about 2.5 mm wide.This dimension enables an operator to align fine lens markings in themiddle of the scribe lines to within 0.25 mm of the desired position.

When the lens is properly positioned, it is then held firmly in place,either manually or mechanically, and molten wax or other adhesivematerial is introduced into the space between the lens front surface andthe hollowed out surface 308 on the block through a bore 301. FIG. 18shows the lens blank 310 mounted to the block 300 after wax has beenejected into the hollow interior. After the wax cools, the securelyblocked lens blank is mounted on the machining platform for edging andback surface generation.

FIG. 19 is a schematic representation of an alternative exemplaryblocking method and blocking system of the present invention. Here theblocking system 230 comprises a block 229 that includes a semicircularmounting ring or rim 232 that is a known height above the origin plane234 of the blocking system. The radius of the semicircular mounting rim232 is known and the top plane of the ring is parallel to the referenceplane 234 of the blocking system.

When blocking either spherical or aspherical front surface lens blanks,the point 238 on the lens blank 236 that will occupy the geometriccenter of the frame when the lens is finished, is positioned directlyover the origin 240 of the blocking system 230. The point 238 on thelens 236 so positioned during blocking will end up in the geometriccenter of the lens after edging. In addition the front surface 242 isorientated so that it is generally parallel to the reference plane 234of the blocking system. When the lens blank 236 is mounted or blocked inthis manner, the computer 102 is operative to calculate or extrapolatefrom a data store the coordinate (x,y,z) of any point on the lenssurface relative to the origin of the lens blocking system 230. That is,the z-value can be determined for any chosen x,y location relative tothe origin 240 of the blocking system.

The exemplary blocking system as shown in FIG. 19 is operative to bond alens blank 242 securely to the block 229 by injecting a wax or otheradhesive material into a cavity 244 of the block 229 that is locatedadjacent the front surface of the blocked lens blank 242. When the waxhardens the resulting bond between the lens blank 242 and the block 229is sufficient to hold the lens blank in place during the edging andsurfacing operations.

In one exemplary embodiment of the present invention the block may beselected from a library of several dozen shapes and sizes of blocks thatmost closely resembles the finished lens in size and shape while stillbeing smaller than the finished lens. Selecting a block for the lensblank with roughly the same size and shape but slightly smaller than thefinal lens gives support to the entire lens surface to minimize thebending and flexing of the lens during the surfacing and fining andpolishing processes, thereby eliminating optical errors. In additionsuch a block will not come into contact with a tool while edging sinceit is slightly smaller than the finished lens. When a lens is blocked inthe previously described methods, all spatial coordinate points (x,y,z)of the lens blank's front surface are known relative to the coordinatesystem of the machining platform. With knowledge of the position ofevery point on the lens front surface relative to the coordinate systemof the machining platform, it is possible to calculate tool paths toperform both the edging and surfacing of the lens with a properlyconfigured tool.

FIG. 20 shows an exemplary machining platform 600 that is operative toconcurrently surface and edge two ophthalmic lenses. The exemplarymachining platform 600 is further operative to machine both customblocks for blocking lens blanks and both surface lap tools for polishingand fining ophthalmic lenses generated by the machining platform.

The exemplary machining platform 600 includes an articulation shaft 602and a mounting stage 604 in operative connection with the articulationshaft 602. In the exemplary embodiment a computer system of the presentinvention is operative to selectively rotate the articulation shaft 602to raise or lower the position of the mounting stage 604. The exemplarymounting stage 604 includes an arbor 606 which is selectively rotatableresponsive to the computer processor. The arbor 606 is operative toreceive two mounting blocks 608, 610 positioned at opposed ends of thearbor.

The machining platform 600 further comprises at least one ball slidecarriage 612, at least two machining tools 614, 616 and two spindlemotors 618, 620. The spindle motors are in operative connection with theat least one ball slide carriage 612 and are positioned adjacent theopposed ends of the arbor 606. Each tool 614, 616 is in releasableconnection with a spindle motor 618, 620. The spindle motors areoperative to rotate the tools and are independently operative responsiveto the computer processor to move toward and away from the arbor endsalong the ball slide carriage 612. In the exemplary embodiment thearticulation shaft is turned by a planetary gear motor 622 mounted onthe end of the articulation shaft 602. The arbor 606 is turned by theright angle gear motor 624 responsive to the computer processor.

In the exemplary embodiment of the machining platform 600, the computerprocessor is operative to selectively move the machining tools 614, 616relative the ends of the arbor 606 through a plurality of tool paths formachining custom blocks, surfacing and edging lens blanks, and surfacinglap tools. In addition to machining two lens simultaneously, two laptools simultaneously, or two mounting blocks simultaneously, theexemplary embodiment of the machining platform may further be used tosimultaneously machine both a block and a lap tool for a particularlens. In addition the exemplary machine may be used to simultaneouslymachine a lens and a corresponding lap tool for the lens.

FIG. 21 shows the exemplary machining platform 600 in a configurationthat enables an operator to more easily mount and remove blocks, laptools and lenses from the machine platform. Here the articulation shaftarbor 606 responsive to the computer processor has rotated the mountingstage 604 upwardly to move the arbor 606 away from the machining tools614, 616. In this exemplary orientation, the tools 614, 616 may also bemore easily removed.

An alternative exemplary embodiment of a machining platform for thepresent invention is shown in FIGS. 22-24. FIG. 22 shows a top plan viewof the machining platform 400 and FIG. 23 shows a front view of themachining platform 400. The machining platform 400 includes an arbor 402mounted on a mounting stage 404. The arbor 402 is rotated by aservo-motor 412 in operative connection with the arbor.

The arbor 402 is operative to receive two blocked lens blanks 406 and408 on opposed ends of the arbor 402. By selectively rotating the arborwith the servo motor 412, the angular orientation of the lenses can bechanged.

The machining platform also includes two spindles 414 and 416, withtools 418 and 419 that are positioned adjacent to each of the lensblanks 406 and 408. In this described exemplary embodiment the axis ofrotation of the tools 418 and 419 is orientated parallel to the axis ofrotation of the arbor shaft. However, in other alternative embodimentsother angular relationships between the spindles and arbor shaft may beused depending on the shape of the machining tool and the type ofmachining operation being performed.

Each of the spindles 414 and 416 is operative to move independently ofeach other toward and away from the lens blanks 406 and 408respectively. This enables the machining platform to machine the backsurfaces of the lens blanks simultaneously according to differentprescription specifications for each lens being generated.

FIG. 24 shows a side view of machining platform 400. As shown in FIG. 24the machining platform is operative to selectively move the arbor in aplane perpendicular to the axis of rotation of the arbor shaft. In thisdescribed exemplary embodiment this is accomplished by having themounting stage pivot at pivot point 432 of a pivot support 428. Theamount of pivot angular rotation is selectively controlled by astage-moving device 420.

In this described exemplary embodiment the stage moving device 420includes a ball slide 422 in operative connection with an end portion426 of the mounting stage. The ball slide 422 is selectively drivenalong a ball screw 423 with a servo motor 424 that is operativelyconfigured to selectively rotate the ball screw 423. The end portion 426of the mounting stage moves up or down responsive to the movement of theball slide 422. As a result the angular position of the mounting stage404 can be selectively adjusted to move the arbor 402 and the lensblanks 406 and 408 relative to the machining tools.

In this described exemplary embodiment the pivot point 432 is locatedbetween the stage moving device 420 and the arbor 402. However, inalternative embodiments the arbor 402 may be located between the pivotpoint 432 and the stage moving device 420 or the stage moving device 420may be located between the pivot point 432 and the arbor 402.

The mounting stage may also include an encoder 430 at the pivot point432 that is operative to measure the amount of angular rotation of themounting stage relative the pivot support 428. Alternatively, a linearencoder could be used to monitor the linear position of a portion of themounting stage. The feedback output of the encoder is used by themachining platform to control the operation of the servo motor of thestage moving device. This enables the system to accurately place thearbor in the proper position for machining the lens blanks according tothe calculated tool paths.

FIG. 25 shows a schematic view of a farther alternative exemplaryembodiment of a machining platform of the present invention. Here themachining platform 170 includes two mounting stages 172 and 174 uponwhich blocked semi-finished lenses are mounted for back surfacegenerating and edging, and upon which reusable lap tools are mounted forsurfacing. With two mounting stages, both right and left lenses 176 and178 are surfaced and edged at the same time. Similarly both the rightand left mounting blocks and right and left lap tools for lenses 176 and178 may also be surfaced simultaneously with machining platform 170.

In this described embodiment the machining platform 170 includes anx-axis ball slide 190 and two y-axis ball slides 192 and 194. The x-axisball slide comprises a servo or stepper motor 184, a right handed ballscrew 182, a flexible coupling 186, and a left handed ball screw 18. Themounting stage 174 for right lenses and right lap tools is driven by theleft handed ball screw 180 and the mounting stage 172 for left lensesand left lap tools is driven by the right handed ball screw 182. The twostages 172 and 174 travel along the x-axis in synchronized opposingmotion. The two ball screws are in operative connection with a flexibleconnector which couples the motion of the right-handed ball screw thatis in direct connection with the drive motor with the motion of theleft-handed ball screw. This arrangement enables the single motor 184 todrive both mounting stages 172 and 174 in coordinated opposing motion.

As shown in FIG. 26, the single x-axis ball slide 190 is mounted on thetwo parallel y-axis ball slides 192 and 194 so both stages always movetogether in the y-axis. The y-axis ball slides 192 and 194 are alsodriven by a single servo or stepper motor (not shown). With thisexemplary configuration, when one stage performs a circular motion inthe x-y plane moving clockwise, the other stage performs precisely thesame circular motion but moving counterclockwise.

In this described embodiment, the machining platform includes two highspeed spindles 208 and 210 with corresponding tools 200 and 202. Spindle208 for machining a left lens or left lap tool is in operativeconnection with a left z-axis ball slide 204. Spindle 210 for machininga right lens or right lap tool is in operative connections with a rightz-axis ball slide 206. The two stages 172 and 174 move under the z-axisspindles 208 and 210 for simultaneous edging of both right and leftlenses and for simultaneous surfacing of both right and left lenses. Thetwo z-axis ball slides 204 and 206 are positioned generallyperpendicular to the two y-axis ball slides 192 and 194. The z-axisposition of each spindle tool is driven by its own servo motor orstepping motor 212 and 214. The motion of one tool can be and usually isindependent of the other tool.

For all the described embodiments, the tools should rotate in oppositedirections for the best results. Consequently, the tools affixed to eachspindle require right or left isometric edge configurations appropriatefor its spindle rotational direction and normal tool path direction.This allows both tools to cut uphill at the same time with conventionalmilling. Without opposing rotation, one spindle would be performingconventional milling while the other would be performing so called“climb” cutting. This opposing rotational direction is necessary inorder to get similar finishes on the edges of the lenses. As discussedpreviously exemplary embodiments of the present invention are operativeto block lens blanks on the geometric center of the finished lens suchthat the normal of the front surface at the geometric center of thefinished lens is parallel to the relative feed axis of the edging tool.Such a blocking system is optimized for the edging of the lens blank.However, as discussed previously, geometric center blocking may resultin an optical center of the lens which moves or “creeps” as the lens ismade to decrease in thickness during fining. In order to use this modeof blocking for surface generation as well as edging, the exemplarymachining platform of the present invention is operative to compensatefor this optical center “creep” when calculating surface generation toolpaths. In the exemplary embodiment tool paths are calculated whichproduce a back surface with an optical center position and/or thicknessthat are offset in order to compensate for the amount of expectedoptical center creep produced during fining. As a result, when the lensis fined, the optical center will “creep” onto the correct position atthe completion of fining.

When calculating for edging tool paths for spherical front surfaceblanks, the “sagittal depth formula” is used and a constant is added torepresent how far the eyewire bevel (or groove) on the lens should befrom the front surface of the lens (bevel offset), a z-value iscalculated for each x,y coordinate in the array of points. From thisoperation a three dimensional array of points representing the shape ofthe lens and the position of the eyewire bevel or groove is produced.This set of x,y,z points is then used to calculate a tool pathencompassing all these points in succession. Standard CNC machiningtechniques are applied to compensate for the radius of the tool beingused and to generate tool paths for roughing passes before the final cutis performed.

Aspheric front surface lenses like Progressive Add Lenses (PAL's) orExecutive type multifocals are treated differently than spherical frontsurface lenses when calculating tool paths for surfacing and edging.Instead of calculating the z-value for each x,y point as described aboveusing the sagittal depth formula, a z-value for any x,y position on thelens is accurately extrapolated from a database or data file containingtopographical information about the lens front surface. Lens frontsurface topographical coordinates can be gathered to produce thesedatabases or data files using either non-contacting techniques or byphysical probing techniques.

Aspheric front surface lens blanks are blocked just as spherical frontsurface lens blanks are blocked. The point on the lens that will occupythe geometric center of the frame receiving aperture is positioned so asto correspond to the origin of the blocking system. Rather than usingthe sagittal depth formula, the x-y-z coordinates of the back surfaceare calculated responsive to the stored topographical coordinates thatcorrespond to the front surface. It should be noted that spherical frontsurface lenses may also be treated in this same fashion rather thanusing sagittal depth calculations.

Current systems for acquiring front surface scans for aspherical frontsurface lens blanks are prohibitively expensive for most surfacinglaboratories. However, the present exemplary method and system formachining ophthalmic lenses does not require that each aspherical frontsurface lens blank be scanned prior to machining. Instead each lens typeneeds only be scanned once and the data stored in a database or onphysical media such as CD's or DVD'S. The scanned data can be madeavailable to many optical laboratories through distribution of CD's orDVD's or made available via download from a web site on the Internet,for example. These data stores are operative to return a set of relative“z” values for any set of “x,y” coordinate queries for any specific lenstype. These data stores may also hold other information about the lensblank including the location of factory markings or other lenslandmarks, the index of refraction of the lens material, the edge andcenter thicknesses of the blank, and the lens blank diameter.

Acquiring the data in the optical laboratory through distribution is atpresent less costly and less complicated than acquiring and employingsurface scanners at the optical laboratory site. However, this maychange if surface scanning devices become more cost effective and easierto use. If this should occur, an alternative embodiment of the inventioncould then employ such a surface scanner to acquire the front surfacetopographical data of a lens blank. The scanning device could thencapture an array of x,y,z points describing the front surface topographyrelative to the blocking mechanism and therefore relative to themachining platform coordinate system.

The back surfaces of ophthalmic lenses are either spherical or toric.Spherical surfaces can be thought of as special cases of toric surfaceswhere the radii of the major and minor meridians are equal. Therefore,all lens back surfaces can be considered to be toric. The radii andaxial positions of the major and minor meridians of the back surfacetoric surface can be calculated from prescription data according to theformulae well known in the art. Once these radii are known, it ispossible to calculate the z-value of any point on the back surfacerelative to the back surface apex (e.g. the forward most point on thelens back surface).

Surfacing of the back surfaces of the lens is done using the radiusedend of the rotary tools. The tool paths for these radiused end tools aredefined by the motion made by the center of curvature of the radiusedends of the tool. The tool path taken for surfacing a toric surface liesentirely within another toric surface. The radii of the major and minormeridians of the tool path torus differ from the radii of the major andminor meridians of the toric surface respectively by the length of theradius of curvature of the tool end. For a concave toric surface theradius of the major meridian of the tool path torus is equal to theradius of the major meridian of the surface minus the length of theradius of the tool. Likewise, the radius of the minor meridian of thetool path torus is equal to the radius on the minor meridian of thesurface minus the length of the radius of the tool. The tool path needsto pass through enough of the points of the tool path torus to generatea surface smooth enough for fining in a standard system.

Calculation of the tool path torus for cutting the convex toric surfacesof lap tools is similar to the concave surface calculations except thatthe major and minor meridian radii of the tool path torus are longerthan the major and minor radii of the toric surface respectively by thetool radius minus the thickness of the fining and polishing pads used inorder to be properly compensated for the thickness of the fining andpolishing pads.

In the exemplary embodiment of this invention, the lap tool surfaces andthe machineable layer of the blocks are made from the same low meltingpoint wax that is used to block the lenses. Other low melting pointsubstances could be adapted to serve the same purpose such as athermoplastic material, a metallic alloy or any other material that maybe machined by the machining platform. A substrate of this low meltingpoint wax or other material is applied fairly thickly to the base ofeach lap tool and block. Alternately, disposable machinable materials ofvarious composition could be employed as the lap tool or the mountingblock substrate. Unless a lap tool library is employed, each lens thatis surfaced requires the preparation of its own lap tool (if fining andpolishing are required) and mounting block.

Thus the system and method for ophthalmic lens manufacture achieves theabove stated objectives, eliminates difficulties encountered in the useof prior devices and systems, solves problems and attains the desirableresults described herein.

In the foregoing description certain terms have been used for brevity,clarity and understanding, however no unnecessary limitations are to beimplied therefrom because such terms are used for descriptive purposesand are intended to be broadly construed. Moreover, the descriptions andillustrations herein are by way of examples and the invention is notlimited to the exact details shown and described.

In the following claims any feature described as a means for performinga function shall be construed as encompassing any means known to thoseskilled in the art to be capable of performing the recited function, andshall not be limited to the structures shown herein or mere equivalentsthereof.

Having described the features, discoveries and principles of theinvention, the manner in which it is constructed and operated, and theadvantages and useful results attained; the new and useful structures,devices, elements, arrangements, parts, combinations, systems,equipment, operations, methods and relationships are set forth in theappended claims.

We claim:
 1. A method for machining an ophthalmic lens from a lens blankcomprising the steps of: a) machining a lens mounting block with amachining platform responsive to the front surface topography of a lensblank; b) mounting the lens blank to the mounting block; and c)performing machining operations on the lens blank with the machiningplatform.
 2. The method according to claim 1, wherein in step (c) themachining operations on the lens blank include edging and back surfacegeneration of the lens blank.
 3. The method according to claim 1,further comprising: d) providing data representative of the physicalproperties of the lens blank including data representative of the frontsurface topography of the lens blank; e) providing data representativeof a lens receiving portion of a spectacle frame; and f) providing datarepresentative of an ophthalmic lens prescription specification; g)formulating a plurality of tool paths responsive to the datarepresentative of the physical properties of the lens blank, the datarepresentative of lens receiving portion of a spectacle frame, and datarepresentative of an ophthalmic lens prescription specification; andwherein in step (a) the mounting block is machined responsive to thetool paths.
 4. The method according to claim 2, further comprising: d)providing data representative of the physical properties of the lensblank including data representative of the front surface topography ofthe lens blank; e) providing data representative of a lens receivingportion of a spectacle frame; and f) providing data representative of anophthalmic lens prescription specification; g) formulating a pluralityof tool paths responsive to the data representative of the physicalproperties of the lens blank, the data representative of lens receivingportion of a spectacle frame, and data representative of an ophthalmiclens prescription specification; and wherein in step (a) the mountingblock is machined responsive to the tool paths.
 5. The method accordingto claim 3, wherein step (a) includes machining at least one portion ofa surface of the mounting block to include a curvature that correspondsto the topography of the front surface of the lens blank, wherein instep (b) the at least one portion of the surface of the mounting blocksupportingly receives the front surface of the lens blank.
 6. The methodaccording to claim 4, wherein step (a) includes machining at least oneportion of a surface of the mounting block to include a curvature thatcorresponds to the topography of the front surface of the lens blank,wherein in step (b) the at least one portion of the surface of themounting block supportingly receives the front surface of the lensblank.
 7. The method according to claim 5, wherein the surface of themounting block includes a cavity, and wherein the at least one portionof the surface of the mounting block is in surrounding relation aboutthe cavity, wherein when the front surface of the lens blank is engagedwith the at least one portion of the surface of the mounting block, thecavity does not contact the front surface of the lens, wherein step (b)includes introducing an adhesive within the cavity that is operative tobond the front surface of the lens blank to the mounting block.
 8. Themethod according to claim 6, wherein the surface of the mounting blockincludes a cavity, and wherein the at least one portion of the surfaceof the mounting block is in surrounding relation about the cavity,wherein when the front surface of the lens blank is engaged with the atleast one portion of the surface of the mounting block, the cavity doesnot contact the front surface of the lens, wherein step (b) includesintroducing an adhesive within the cavity that is operative to bond thefront surface of the lens blank to the mounting block.
 9. The methodaccording to claim 3, wherein step (a) includes machining at least onealignment feature in a surface of the mounting block which is operativeto aid an operator with aligning the lens blank on the mounting block,wherein the at least one alignment feature corresponds to at least onelandmark on the lens blank, wherein step (b) includes aligning the atleast one landmark of the lens blank with the at least one alignmentfeature.
 10. The method according to claim 4 wherein step (a) includesmachining at least one alignment feature in a surface of the mountingblock which is operative to aid an operator with aligning the lens blankon the mounting block, wherein the at least one alignment featurecorresponds to at least one landmark on the lens blank, wherein step (b)includes aligning the at least one landmark of the lens blank with theat least one alignment feature.
 11. The method according to claim 5, 6,7, or 8, wherein in step (a) the mounting block is machined such thatwhen the mounting block is mounted to the machining platform themounting block is operative to supportingly receive the lens blank in anorientation in which a direction normal to a front surface of the lensblank at a geometric center of a lens that will be machined from thelens blank to fit within the lens receiving portion of the spectacleframe is about parallel to a relative feed axis of a machining tool ofthe machining platform, wherein in step (b) the lens blank is mounted tothe mounting block in the first orientation.
 12. The method according toclaim 9 or 10, wherein in step (a) the mounting block is machined suchthat when the mounting block is mounted to the machining platform andthe lens blank is mounted to the mounting block with the at least onelandmark of the lens blank aligned with the at least one alignmentfeature, the mounting block is operative to supportingly receive thelens blank in an orientation in which a direction normal to a frontsurface of the lens blank at a geometric center of a lens that will bemachined from the lens blank to fit within the lens receiving portion ofthe spectacle frame is about parallel to a relative feed axis of amachining tool of the machining platform.
 13. The method according toclaim 1, further comprising: d) providing data representative of thephysical properties of the lens blank including data representative ofthe front surface topography of the lens blank; e) providing datarepresentative of an ophthalmic lens prescription specification; f)providing data representative of a lens receiving portion of a spectacleframe; and g) formulating a plurality of tool paths responsive to thedata representative of the physical properties of the lens blank, thedata representative of the ophthalmic lens prescription specification,and the data representative of a lens receiving portion of a spectacleframe; and wherein in step (c) the machining operations are performed onthe lens blank responsive to the tool paths.
 14. The method according toclaim 2, further comprising: d) providing data representative of thephysical properties of the lens blank including data representative ofthe front surface topography of the lens blank; e) providing datarepresentative of an ophthalmic lens prescription specification; f)providing data representative of a lens receiving portion of a spectacleframe; and g) formulating a plurality of tool paths responsive to thedata representative of the physical properties of the lens blank, thedata representative of the ophthalmic lens prescription specification,and the data representative of a lens receiving portion of a spectacleframe; and wherein in step (c) the machining operations are performed onthe lens blank responsive to the tool paths.
 15. The method according toclaim 1 or 2, wherein in step (c) the machining operations on the lensblank include back surface generation of the lens blank.
 16. The methodaccording to claim 1 or 2, wherein in step (c) the machining operationson the lens blank include edging the lens blank.
 17. The methodaccording to claim 1, wherein in step (c) the machining operations onthe lens blank include edging and back surface generation of the lensblank.
 18. The method according to claim 1, wherein in step (c) themachining operations on the lens blank are performed with a machiningtool, wherein prior to step (b) further comprising: d) determining alocation of a point on the lens blank that about corresponds to ageometric center of a lens that will be machined from the lens blank tofit within a lens receiving portion of a spectacle frame; and whereinstep (b) includes mounting the lens blank on the mounting block in anorientation in which a direction normal to a front surface of the lensblank at the determined location is about parallel to a relative feedaxis of the machining tool, wherein in step (a) the mounting block ismachined wit alignment features which may be used by a user to visuallyalign the lens blank in the orientation in step (b).
 19. The methodaccording to claim 17, wherein in step (c) the machining operations onthe lens blank are performed with a common tool.
 20. The methodaccording to claim 2, wherein in step (c) the machining operations onthe lens blank are performed with a common tool.
 21. The methodaccording to claim 19, wherein the common tool includes a sphericalradiused end portion that is operative to machine the back surface ofthe lens blank and a side edge portion that is operative to machine anedge contour of the lens blank.
 22. The method according to claim 20,wherein the common tool includes a spherical radiused end portion thatis operative to machine the back surface of the lens blank and a sideedge portion that is operative to machine an edge contour of the lensblank.
 23. The method according to claim 21, wherein the common toolfurther includes a grooving portion that is operative to form a groovein the edge contour of a lens blank.
 24. The method according to claim22, wherein the common tool further includes a grooving portion that isoperative to form a groove in the edge contour of a lens blank.
 25. Themethod according to claim 19, wherein the common tool includes an edgepolishing portion that is operative to polish an edge contour of thelens blank and at least one beveling portion that is operative to applysafety bevels to the edge contour of the lens blank.
 26. The methodaccording to claim 20, wherein the common tool includes an edgepolishing portion that is operative to polish an edge contour of thelens blank and at least one beveling portion that is operative to applysafety bevels to the edge contour of the lens blank.
 27. The methodaccording to claim 1 or 2, wherein step (b) includes placing doublesided adhesive film between the lens blank and the mounting block tobond the lens blank to the mounting block.
 28. The method according toclaim 1 or 2, wherein step (b) includes heating a surface of themounting block, whereby the heated surface of the block is operative toadhesively adhere to the front surface of the lens blank.
 29. The methodaccording to claim 1 or 2, wherein step (b) includes heating the surfaceof the block by directing a light source through the lens blank withappropriate wavelength composition and sufficient intensity to meltportions of a surface of the mounting block, whereby the heated surfaceof the mounting block is operative to adhesively adhere to the frontsurface of the lens blank.
 30. The method according to claim 1 or 2,wherein step (b) includes injecting adhesive material between themounting block and the lens blank that is operative to adhesively attachthe lens blank to the mounting block.
 31. The method according to claim1 wherein in step (a) the mounting block is comprised of a reusablemachineable material.
 32. The method according to claim 2, wherein instep (a) the mounting block is comprised of a reusable machineablematerial.
 33. The method according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 31, or 32, wherein step (a) includes simultaneously machining both aleft mounting block and a right mounting block blank for receiving aleft lens blank and a right lens blank for a common prescription. 34.The method according to claim 1, further comprising: d) mounting a laptool blank to the machining platform; and e) machining the lap tool withthe machining platform to a configuration which is operative to fine orpolish a machined back surface of the lens blank.
 35. The methodaccording to claim 2, further comprising: d) mounting a lap tool blankto the machining platform; and e) machining the lap tool with themachining platform to a configuration which is operative to fine orpolish a machined back surface of the lens blank.
 36. The methodaccording to claim 9 or 10, wherein the at least one alignment featureis machined in a position which minimizes an amount of visual parallaxerror that occurs when performing step (b).
 37. The method according toclaim 7 or 8, wherein in step (a) the mounting block is machined tominimize the volume of the cavity when the lens blank is mounted to themounting block in step (b), whereby the transfer of heat from theblocking medium into the lens blank is minimized.
 38. The methodaccording to claims 1, 2, 7, or 8, wherein in step (a) the mountingblock is machined to provide for uniform heat transfer between themounting block and substantially all of a portion of the lens block thatwill remain after edging of the lens blank to fit within a lensreceiving portion of a spectacle frame.
 39. The method according toclaim 1 or 2, wherein step (c) includes rotating the mounting block,wherein prior to step (b) further comprising: d) determining a locationof a point on the lens blank that about corresponds to a geometriccenter of a lens that will be machined from the lens blank to fit withina lens receiving portion of a spectacle frame; and wherein step (b)includes mounting the lens blank on the mounting block in an orientationin which a direction normal to a front surface of the lens blank at thedetermined location is about parallel to an axis of rotation of theblock in step (c), wherein in step (a) the mounting block is machinedwith alignment features which may be used by a user to visually alignthe lens blank in the orientation in step (b).
 40. A method formachining an ophthalmic lens from a lens blank comprising the steps of:a) machining a block with a machining platform; b) mounting a lens blankon the block in an orientation in which a direction normal to a frontsurface of the lens blank at a geometric center of a lens that will bemachined from the lens blank to fit within a lens receiving portion of aspectacle frame is about parallel to a relative feed axis of a machiningtool when the block is affixed to the machining platform; and c)performing machining operations on the lens blank with the machiningplatform, wherein the machining operations include back surfacegeneration and edging of the lens blank without dismounting andremounting the blocked lens blank between the back surface generationand edging operations.
 41. The method according to claim 40 furthercomprising: d) providing data representative of the physical propertiesof the lens blank including data representative of a front surfacetopography of the lens blank; e) providing data representative of anophthalmic lens prescription specification; f) providing datarepresentative of the lens receiving portion of the spectacle frame; andg) formulating a plurality of tool paths responsive to the datarepresentative of the physical properties of the lens blank, the datarepresentative of the ophthalmic lens prescription specification, andthe data representative of a lens receiving portion of a spectacleframe; and wherein in step (c) the machining operations are performed onthe lens blank responsive to the tool paths.
 42. The method according toclaim 2, 13, 14, 17, 40, or 41, wherein in step (c) the machiningoperations on the lens blank further include edge polishing.
 43. Themethod according to claim 2, 13, 14, 17, 40, or 41, wherein in step (c)the machining operations on the lens blank further include edgepolishing and safety beveling.
 44. The method according to claim 2, 13,14, 17, 40, or 41, wherein in step (c) the machining operations on thelens blank further include safety beveling.
 45. The method according toclaim 40, wherein in step (c) the machining operations on the lens blankare performed with a common tool.
 46. The method according to claim 45,wherein the common tool includes an edge polishing portion that isoperative to polish an edge contour of the lens blank and at least onebeveling portion that is operative to apply safety bevels to the edgecontour of the lens blank.
 47. The method according to claim 45, whereinthe common tool includes a spherical radiused end portion that isoperative to machine the back surface of the lens blank and a side edgeportion that is operative to machine an edge contour of the lens blank.48. The method according to claim 25, 26, or 47, wherein the edgepolishing portion of the common tool is operative to polish the edgecontour of the lens blank without polishing the bevel on the edgecontour of the lens blank.
 49. The method according to claim 47, whereinthe common tool further includes a grooving portion that is operative toform a groove in the edge contour of a lens blank.
 50. The methodaccording to claims 21, 22, 23, 24, 25, 26, 45, 47, or 49, wherein instep (c) the common tool is operative to rotate on an axis that is notparallel to a relative feed axis of the common tool.
 51. The methodaccording to claim 40, further comprising: d) mounting a lap tool blankto the machining platform; and e) machining the lap tool with themachining platform to a configuration which is operative to fine orpolish a machined back surface of the lens blank.
 52. The methodaccording to claims 34, 35, or 51, wherein in step (d) the lap toolblank is comprised of reusable machineable material.
 53. The methodaccording to claims 13, 14, or 41, wherein the tool paths are furtherformulated to compensate for a relocation of an optical center of thelens blank that is caused by machining operations on the lens blankafter step (c).
 54. The method according to claims 1, 2, or 40, whereinstep (c) includes simultaneously machining both a left lens blank and aright lens blank for insertion into a common spectacle frame.
 55. Themethod according to claim 1 or 2, wherein step (c) includes rotating themounting block, wherein an axis of rotation of the mounting block isabout parallel to a relative feed axis of the machining tool.
 56. Asystem for machining an ophthalmic lens from a lens blank comprising: acomputer; at least one tool; and a mounting stage, wherein the mountingstage is operative to supportingly receive a removable block, whereinthe computer is operative to have the at least one cutting tool movewith respect to the block to machine the block responsive to atopography of a front of a lens blank to supportingly receive the lensblank in a first orientation, wherein the computer is further operativeto have the at least one cutting tool move with respect to the lensblank mounted to the block in the first orientation to machine the lensblank.
 57. The system according to claim 56, wherein the computer isresponsive to data which describes the optical properties of the lensblank including data representative of a topography of the front surfaceof the lens blank to machine both the block and the lens blank.
 58. Thesystem according to claim 57, wherein the computer is further responsiveto data which is representative of a lens receiving portion of aspectacle frame to machine both the block and the lens blank.
 59. Thesystem according to claim 58, wherein the computer is further responsiveto data which is representative of an ophthalmic lens prescriptionspecification to machine both the block and the lens blank.
 60. Thesystem according to claim 59, wherein the computer is further operativeto selectively have the block rotate with respect to the mounting stage,wherein when the lens blank is in the first orientation, an axis ofrotation of the block is about parallel to a direction normal to a frontsurface of the lens blank at a geometric center of a lens that will bemachined from the lens blank for mounting within the lens receivingportion of the spectacle frame.
 61. The system according to claim 60,wherein the computer is further operative to have the at least onecutting tool machine alignment features in an upper surface of the blockwhich are operative to aid an operator with mounting the lens blank inthe first orientation.
 62. The system according to claim 61, wherein thecomputer is further operative to selectively have the mounting stagerotate about a further axis that is parallel to the axis of rotation ofthe mounting stage.
 63. The system according to claim 62 wherein the atleast one cutting tool includes a common cutting tool that is operativeto both edge and surface the lens blank, wherein the computer is furtheroperative to have the common cutting tool surface and edge the lensblank.
 64. The system according to claim 62, wherein the mounting stageis operative to receive a removable lap tool blank, wherein the computeris operative to have the at least one cutting tool move with respect tothe lap tool blank to machine the lap tool blank for fining andpolishing a machined back surface of the lens blank.
 65. The systemaccording to claim 60, wherein when the lens blank is in the firstorientation, a relative feed axis of the at least one cutting tool isabout parallel to a direction normal to a front surface of the lensblank at the geometric center of a lens that will be machined from thelens blank for mounting within the lens receiving portion of thespectacle frame.
 66. The system according to claim 65, wherein thecomputer is operative to cause the at least one cutting tool to movetoward and away from the mounting stage along the relative feed axis.67. The system according to claim 62, wherein the mounting stageincludes a shaft, wherein the shaft is operative to sportingly receivetwo removable blocks on opposed ends of the shaft, wherein the computeris operative to selectively rotate the shaft.
 68. The system accordingto claim 67, wherein the mounting stage includes a second shaft parallelto the first shaft, and two cutting tools adjacent the two blocks,wherein the computer is operative to selectively rotate the mountingstage about the second shaft to move the blocks in a transversedirection with respect to the cutting tools.
 69. The system according toclaim 56, wherein the computer is operative to selectively move themounting stage in a plane that is about perpendicular to the at leastone cutting tool.
 70. The system according to claim 69, wherein thecomputer is operative to selectively move the mounting stageindependently along both an x axis and a y axis of the plane.
 71. Thesystem according to claim 56, wherein when the lens blank is in thefirst orientation, a relative feed axis of the at least one cutting toolis about parallel to a direction normal to a front surface of the lensblank at a geometric center of a lens that will be machined from thelens blank for mounting within a lens receiving portion of a spectacleframe.
 72. The system according to claim 56, further comprising a datastore and a graphics tablet in operative connection with the computer,wherein when a user traces the inner circumference of a lens receivingportion of a spectacle frame with the graphics tablet, the computer isoperative to store in the data store a plurality of frame coordinatesthat correspond to trace signals of the graphics tablet that arerepresentative of a size and shape of the lens receiving portion of thespectacle frame.
 73. A method for machining an ophthalmic lens from alens blank comprising the steps of: a) determining a location of a pointon a lens blank that about corresponds to a geometric center of a lensthat will be machined from the lens blank to fit within a lens receivingportion of a spectacle frame; b) mounting the lens blank on a block inan orientation in which a direction normal to a front surface of thelens blank at the determined location is about parallel to a relativefeed axis of a machining tool of a machining platform; and c) performingmachining operations on the lens blank with the machining platform,wherein the machining operations include back surface generationoperations on the lens blank with the machining tool.
 74. A method formachining an ophthalmic lens from a lens blank comprising the steps of:a) determining a location of a point on a lens blank that aboutcorresponds to a geometric center of a lens that will be machined fromthe lens blank to fit within a lens receiving portion of a spectacleframe; b) mounting the lens blank on a block in an orientation in whicha direction normal to a front surface of the lens blank at thedetermined location is about parallel to an axis of rotation of theblock; and c) performing machining operations on the lens blank with themachining platform, wherein the machining operations include backsurface generation operations on the lens blank during rotation of theblock and lens blank by the machining platform about the axis ofrotation of the block.
 75. The method according to claim 73 or 74,wherein prior to step (a) further comprising: d) providing datarepresentative of the lens receiving portion of the spectacle frame; andwherein in step (a) the location of the point is determined responsiveto the data representative of the lens receiving portion of thespectacle frame.
 76. The method according to claim 75, wherein prior tostep (b) further comprising: e) providing data representative of thephysical properties of the lens blank including data representative of afront surface topography of the lens blank; and wherein the lens blankis mounted in step (b) responsive to the data representative of thefront surface topography of the lens blank.
 77. The method according toclaim 76, wherein prior to step (c) further comprising: f) providingdata representative of an ophthalmic lens prescription specification; g)determining a plurality of tool paths responsive to the datarepresentative of the physical properties of the lens blank, the datarepresentative of the ophthalmic lens prescription specification; andwherein in step (c) the machining operations are performed on the lensblank responsive to the tool paths.
 78. The method according to claim77, wherein in step (g) the tool paths are further determined responsiveto the data representative of the lens receiving portion of thespectacle frame, wherein in step (c) the machining operations includeboth the back surface generation and an edging of the lens blank withoutdismounting and remounting the blocked lens blank between the backsurface generation and the edging operations.
 79. The method accordingto claim 78, wherein in step (c) the back surface generation and theedging operations on the lens blank are performed with a common tool.80. The method according to claim 79, wherein the common tool includes aspherical radiused end portion that is operative to machine the backsurface of the lens blank and a side edge portion that is operative tomachine an edge contour of the lens blank.
 81. The method according toclaim 78, wherein the tool paths are further determined to compensatefor a relocation of an optical center of the lens blank that is causedby further machining operations on the lens blank after step (c). 82.The method according to claim 81, wherein after step (c), the lens blankcorresponds to the lens with a back surface and an optical center in afirst position on the lens, wherein further comprising: h) performingfurther machining operations on the back surface of the lens whichcauses the optical center to relocate to a second position on the lens.83. The method according to claim 82, wherein the data representative ofthe ophthalmic lens prescription specification corresponds to a desiredlens having an optical center in a third position, wherein the secondposition of the optical center of the lens in step (h) is closer to thethird position of the optical center for the desired lens than is thefirst position of the optical center of the lens.
 84. The methodaccording to claim 83, wherein in step (h) the further machiningoperations include polishing the back surface of the lens.
 85. Themethod according to claim 73 or 74, wherein prior to step (b) furthercomprising: d) performing machining operations on the block with themachining platform, including machining at least one alignment featurein a surface of the block which is operative to aid an operator withaligning the lens blank on the block, wherein the at least one alignmentfeature corresponds to at least one landmark on the lens blank. 86.Computer readable media bearing instructions which are operative tocause at least one computer in the machine platform to cause themachining platform to carry out the method steps recited in claim 1, 73,or
 74. 87. A system for machining an ophthalmic lens from a lens blankcomprising: at least one computer; at least one tool; and a mountingstage, wherein the mounting stage is operative to support at least oneblock, wherein the at least one computer is operative to cause the atleast one cutting tool to move with respect to the at least one block tomachine the at least one block responsive to a topography of a front ofat least one lens blank to supportingly receive the at least one lensblank in a first orientation, wherein the at least one computer isfurther operative to cause the at least one cutting tool to machinealignment features in an upper surface of the at least one block whichare operative to aid an operator with mounting the at least one lensblank in the first orientation, wherein the at least one computer isfurther operative to cause the at least one cutting tool to move withrespect to the at least one lens blank mounted to the at least one blockin the first orientation to machine the at least one lens blank.
 88. Thesystem according to claim 87, wherein the at least one computer isoperative to determine a location of a point on the at least one lensblank that about corresponds to a geometric center of a lens that willbe machined from the at least one lens blank to fit within a lensreceiving portion of a spectacle frame, wherein when the at least onelens blank is in the first orientation, a direction normal to a frontsurface of the at least one lens blank at the determined location isabout parallel with a relative feed axis of the at least one tool. 89.The system according to claim 87, wherein the at least one computer isoperative to determine a location of a point on the at least one lensblank that about corresponds to a geometric center of a lens that willbe machined from the at least one lens blank to fit within a lensreceiving portion of a spectacle frame, wherein the at least onecomputer is further operative to cause the mounting stage to selectivelyrotate the at least one block, wherein when the at least one lens blankis in the first orientation, a direction normal to a front surface ofthe at least one lens blank at the determined location is about parallelwith an axis of rotation of the at least one block.
 90. The methodaccording to claim 39, 60, 74, or 89, wherein when the lens blank ismounted to the black, the axis of rotation of the block about intersectsthe geometric center of the lens.